STRUCTURAL GEOLOGY OF FAST-MOVING GLACIERS—DISCRIMINATION OF DYNAMIC TYPES

Fast-moving glaciers are sensitive indicators of regional or global climatic change, they play key roles in any scenario of potential break-up of the large polar ice sheets on Earth. However, the relationship between climatic and glacial change is not straightforward, because fast-moving glaciers in particular exhibit large dynamic changes unrelated to climate. So, it is crucial to distinguish between dynamic and climatic effects when studying mass changes in glaciers.

Traditional glaciologic investigation is focused on measurements of velocity, strain rate, and surface height and flow modeling using continuum mechanics. However, these measurements are time-consuming and costly and therefore very limited in coverage. Therefore, we developed a different approach to characterize the dynamic type of a glacier utilizing structural analysis of the inventory of brittle-deformation features on the surface based on remote-sensing data such as aerial photography and videography and satellite data. Characteristic structural patterns are identified, defined, kinematically analyzed and classified. This allows for segmentation and mapping of the glacier surface into structural provinces. The occurrence of certain structural patterns as well as the distribution of structural patterns form a solid basis for the discrimination of different dynamic types, such as continuously fast-moving ice streams, surge glaciers, fast-moving outlet glaciers, slow-moving valley glaciers, among others.

Examples are presented from Jakobshavns Isbrae, West Greenland,(continuously fast-moving ice stream), Bering Glacier, Alaska, (surge glacier), Helheimgletscher, East Greenland, (complex outlet glacier), and Fenrisgletscher, East Greenland, (slow-moving valley glacier).